Re: [PATCH net-next v6 6/9] net: dsa: lan9645x: add vlan support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] lan9645x_port_vlan_filtering clobbers the CPU (NPI) port's egress tagging configuration
--

commit 6fffecbf30e0b6af9ee79a8cd06c0280fc266991
Author: Jens Emil Schulz Østergaard <jensemil.schulzostergaard@microchip.com>

    net: dsa: lan9645x: add vlan support
    
    Add VLAN support for VLAN-aware and VLAN-unaware bridges.

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c
> index 9d8f3a1b335bd..eb13dfadbd3cf 100644
> --- a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c
[ ... ]
> @@ -559,11 +563,52 @@ static void lan9645x_port_bridge_leave(struct dsa_switch *ds, int port,
[ ... ]
> +static int lan9645x_port_vlan_filtering(struct dsa_switch *ds, int port,
> +					bool enabled,
> +					struct netlink_ext_ack *extack)
> +{
> +	struct lan9645x *lan9645x = ds->priv;
> +	struct lan9645x_port *p;
> +
> +	p = lan9645x_to_port(lan9645x, port);
> +	p->vlan_aware = enabled;
> +	lan9645x_vlan_port_apply(p);

[Severity: High]
Does this code inadvertently clobber the CPU (NPI) port's egress tagging
configuration?

When VLAN filtering is toggled on a user bridge port, the DSA core
synchronizes this state to the CPU port by calling port_vlan_filtering().
Here, the driver unconditionally delegates to lan9645x_vlan_port_apply(),
which executes both ingress and egress VLAN application:

lan9645x_vlan_port_apply() {
        lan9645x_vlan_port_apply_ingress(p);
        lan9645x_vlan_port_apply_egress(p, NULL);
}

Because the CPU port is typically non-bridged,
lan9645x_vlan_port_apply_egress() will overwrite the REW_TAG_CFG register
with LAN9645X_TAG_NO_PVID_NO_UNAWARE:

lan9645x_vlan_port_apply_egress() {
        ...
        if (!lan9645x_port_is_bridged(p)) {
                tag_cfg = LAN9645X_TAG_NO_PVID_NO_UNAWARE;
        ...
}

The driver correctly avoids applying egress tagging to the CPU port in other
places. For example, lan9645x_port_setup() explicitly skips
lan9645x_vlan_set_hostmode() for the NPI port, and
lan9645x_vlan_cpu_add/del() only update ingress state.

Without a similar guard (such as checking p->chip_port != lan9645x->npi) in
this function, toggling VLAN filtering might push unexpected 802.1Q tags
onto frames extracted to the host, breaking DSA tag parsing and software
forwarding.

> +
> +	return 0;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527-dsa_lan9645x_switch_driver_base-v6-0-4d409ae64f3c@microchip.com?part=6